Why is the mixing volume, of sounds we add to XACT, -12.0dB the default?

If I leave everything at this default setting, my game volume is very low.  Is it typical to adjust all these volumes back to 0.0dB (louder, normal volume)?

Matthew Doucette:

Why is the mixing volume, of sounds we add to XACT, -12.0dB the default?

Short answer: Because in professional audio recording, the nominal dynamic range is 18 dB, and the top of the scale in XACT is +6 dB. +6 minus 18 is -12.

Long answer: Decibels are relative. When you say something is "0 dB", that's meaningless until you identify a reference point. The reference point for XACT is the professional audio track, which is normally mixed to a -6 dB peak RMS - which is to say, if you amplified this track more than 6 dB, it would exceed the physical capabilities of the recording equipment. Exceed by a little, and you get some distortion. Exceed by a lot, you get what sounds like static. Exceed by a whole lot, and you can do serious damage to very expensive kit. So because the reference point is expected to be at -6 dB, XACT sets the top of the scale at... well, the top of the scale. The dynamic range is established by the history of multitrack recording - when you mix lots of tracks together, you need a certain amount of "room" so they don't cause too much distortion when summed in the final mixdown. For most purposes, 18 dB is about right - this has been established by a century of audio and film recording, and has little "hard" science behind it, because there was no science of film and audio in the early days. You did whatever felt right, and over the years thousands of people converged on the right answer just by guessing.

Because you need headroom. When you add two uncorrelated signals of the same loudness, the average overall loudness goes up by 3 dB, but the peak may actually go up by 6 dB. Clipping (over-peaking) in digital audio sounds like absolute crap.

So, add two full-scale sounds at -12, and you get peaks at -6. Add four, and you get peaks at 0. Add eight, and you get peaks at +6, which will be clipping in the XACT library. You also need some headroom to allow for parameters that vary the volume and pitch. I find that -12 dB is a good place to start, but some sounds need more, and others less. It also matters how loud/compressed your source sounds are -- if they are heavily compressed and normalized, -12 dB is actually pretty loud; if they are sparser and not full scale, it's pretty soft. That's why you can play more than one sound at the same time and hear how they mix.

Awesome, I perfectly understand the concept of needing headroom and dynamic range.

So, I guess the question is... my game is sounding very quiet compared to Windows sounds, Winamp, etc., so should I amateurly bump up all my sounds to 0.0dB (or close) in XACT until my game audio "matches" the rest of my Windows environment?  The way it is now, even though it has lots of range waiting, is far too quiet.  When I quit my game, and hear a Windows error beep, it blasts my ears off!

I'd suggest bumping the sounds up a few db at time, until it sounds about right. If you ever hear distortion, you have gone too far and should back things down a bit. If you have a couple of sounds that are a lot louder than other sounds you are using, don't raise them up as much (unless you have a good reason why they are louder).

Another issue might be sounds themselves. Sounds that have been normalized when they are created are basically "full volume", but sounds can certainly be inherently quiet, depending on how they were produced. If you have sounds that are starting out quiet, you can certainly use XACT to boost them a fair amount.

Hey Matt, I recently had the same problem with sounds that were WAY too quiet.  I tried bumping up the volume range to +6 in XAct (being completely ignorant of what that meant before reading this very helpful thread) and it still wasn't enough.  Problem was, I knew the effects I was using came from a professional audio guy.  Turns out they were coming in too quiet because of having my headphones set on 5.1 surround.  I turned it down to a regular 4-speaker (or 2-speaker, etc.) and my sounds started coming in nice and loud.

I don't know if that's at all relavent to you or anyone else that may run across this problem, but I thought I'd mention it just in case.

rbuhrRI:

Hey Matt, I recently had the same problem with sounds that were WAY too quiet.  I tried bumping up the volume range to +6 in XAct (being completely ignorant of what that meant before reading this very helpful thread) and it still wasn't enough.  Problem was, I knew the effects I was using came from a professional audio guy.  Turns out they were coming in too quiet because of having my headphones set on 5.1 surround.  I turned it down to a regular 4-speaker (or 2-speaker, etc.) and my sounds started coming in nice and loud.

I don't know if that's at all relavent to you or anyone else that may run across this problem, but I thought I'd mention it just in case.

Well I appreciate it.  Thank you.  If that was your issue, then all games and sounds on your system should have been too quiet, too.  Were they?  My system is set for headphones and 2-speakers, I change it back and forth in my Windows sound settings.  But regardless of that, I noticed that every other sound on my Windows system was so much louder than my game, such as Windows sounds, youtube, other games, etc.  I just bumped up my sounds to +6 I believe, and that was an approximation which brought my game to approximately the same loudness.  Seems to have worked without hitting into distortion!

Matthew Doucette:

If that was your issue, then all games and sounds on your system should have been too quiet, too.  Were they?

See, that's the weird thing.  All my Windows sounds and music were coming in just fine when it was set on 5.1 surround.  But I did notice that some sound effects in some games, particularly those that are not 3D-positioned sounds, come in extremely faintly (almost undetectable even.)  I suspect it's because some sound effects get piped into some kind of a secondary or tertiary channel by default in 5.1 when they don't actually support that format.  But then again, I'm extremely unknowledgeable when it comes to all things audio.

If the source is stereo, then it will play fine even if you have set it to 5.1 but listen in stereo.

The XNA games detect if your output is set to 5.1, and if so, makes a 5.1 source, which won't work well when you only listen in stereo. The fix is, as you discovered, to configure output as 2 speakers, which means XNA will create a 2-channel source.

I finally got a chance to test out my game (Duality: ZF) on my home stereo, off my Xbox, and it's a tad bit louder than other games!  I set all my sounds to +0.0dB in XACT, and then adjusted sound effects that were too overbearing lower.  The music just pounds!  I hope this is not too much of a score-reducer in the contest.  On my PC, it sounded fine.

We started so late, that we had little to no beta testing on home setups.